1. Field of the Invention
The present invention relates to a method of manufacturing a semiconductor device wherein a high concentration diffusion layer is formed by an ion implantation method, and particularly to a method of. realizing a high concentration diffusion layer free of crystal lattice defects.
2. Description of the Related Art
When manufacturing a semiconductor device, an ion implantation method has heretofore been widely used as a technology for introducing electrically active impurities. An impurity semiconductor needs to have introduced impurities serving as dopant into a semiconductor material. The ion implantation method is used as one of the introducing methods.
Since, for example, high energy ions are injected into a semiconductor crystal in the ion implantation method, crystal lattice defects occur due to collisions between the ions and a crystal lattice, so that crystallizability is broken. Therefore, ion implantation has been performed through a mask film such as a silicon oxide film or the like to reduce damage to a crystal or the like (see Japanese Patent Publication Laid-Open No. Hei 5(1993)-211165). Further, high-temperature heat treatment is done to recover the crystallizability. Simultaneously, the electrical activation of implanted dopant impurity atoms has been carried out.
Since, however, damage to a silicon substrate crystal is serious in the case of ion implantation of a source/drain or the like increased in dose in a silicon semiconductor device, for example, there is a need to perform post-ion implantation heat treatment at a high temperature or for a long time in order to promote damage recovery. However, such heat treatment diffuses a dopant impurity more than necessary. Thus, a problem such as a short channel effect or the like will arise in a micro device. It is therefore difficult to sufficiently recover crystal lattice defects without any problem.